The Death of a Star - How Stars Work | HowStuffWorks The Death of a Star Photo courtesy of NASA /Space Telescope Science Institute Hubble Space Telescope photograph of the Rotten Egg planetary nebula Several billion years after its life starts, a star will die. How the star dies, however, depends on what type of star it is. Stars Like the Sun When the core runs out of hydrogen fuel, it will contract under the weight of gravity. However, some hydrogen fusion will occur in the upper layers. As the core contracts, it heats up. This heats the upper layers, causing them to expand. As the outer layers expand, the radius of the star will increase and it will become a red giant. The radius of the red giant sun will be just beyond the Earth's orbit. At some point after this, the core will become hot enough to cause the helium to fuse into carbon. When the helium fuel runs out, the core will expand and cool. The upper layers will expand and eject material that will collect around the dying star to form a planetary nebula. Finally, the core will cool into a white dwarf and then eventually into a black dwarf. This entire process will take a few billion years.

Photo courtesy of NASA /Space Telescope Science Institute Hubble Space Telescope photograph of the rings around Supernova 1987A Stars More Massive Than the Sun When the core runs out of hydrogen, these stars fuse helium into carbon just like the Sun. However, after the helium is gone, their mass is enough to fuse carbon into heavier elements such as oxygen, neon, silicon, magnesium, sulfur and iron. Once the core has turned to iron, it can burn no longer. The star collapses by its own gravity and the iron core heats up. The core becomes so tightly packed that protons and electrons merge to form neutrons. In less than a second, the iron core, which is about the size of the Earth, shrinks to a neutron core with a radius of about 6 miles (10 kilometers). The outer layers of the star fall inward on the neutron core, thereby crushing it further. The core heats to billions of degrees and explodes (supernova), thereby releasing large amounts of energy and material into space. The shock wave from the supernova can initiate star formation in other interstellar clouds. The remains of the core can form a neutron star or a black hole depending upon the mass of the original star.

Up Next Star Facts: The Basics of Star Names and Stellar Evolution Star Facts: The Basics of Star Names and Stellar Evolution By Charles Q. Choi, Space.com Contributor | December 16, 2014 09:41pm ET MORE Credit: University of Leicester Stars are giant, luminous spheres of plasma. There are billions of them — including our own sun — in the Milky Way Galaxy. And there are billions of galaxies in the universe. So far, we have learned that hundreds also have planets orbiting them. History of observations Since the dawn of recorded civilization, stars played a key role in religion and proved vital to navigation. Astronomy , the study of the heavens, may be the most ancient of the sciences. The invention of the telescope and the discovery of the laws of motion and gravity in the 17th century prompted the realization that stars were just like the sun, all obeying the same laws of physics. In the 19th century, photography and spectroscopy — the study of the wavelengths of light that objects emit — made it possible to investigate the compositions and motions of stars from afar, leading to the development of astrophysics.

In 1937, the first radio telescope was built, enabling astronomers to detect otherwise invisible radiation from stars. In 1990, the first space-based optical telescope, the Hubble Space Telescope , was launched, providing the deepest, most detailed visible-light view of the universe. Star naming Ancient cultures saw patterns in the heavens that resembled people, animals or common objects — constellations that came to represent figures from myth, such as Orion the Hunter, a hero in Greek mythology. Astronomers now often use constellations in the naming of stars. The International Astronomical Union, the world authority for assigning names to celestial objects, officially recognizes 88 constellations . Usually, the brightest star in a constellation has "alpha," the first letter of the Greek alphabet, as part of its scientific name. The second brightest star in a constellation is typically designated "beta," the third brightest "gamma," and so on until all the Greek letters are used, after which numerical designations follow. A number of stars have possessed names since antiquity — Betelgeuse , for instance, means "the hand (or the armpit) of the giant" in Arabic.

It is the brightest star in Orion, and its scientific name is Alpha Orionis. Also, different astronomers over the years have compiled star catalogs that use unique numbering systems. The Henry Draper Catalog, named after a pioneer in astrophotography, provides spectral classification and rough positions for 272,150 stars and has been widely used of by the astronomical community for over half a century. The catalog designates Betelgeuse as HD 39801. Since there are so many stars in the universe, the IAU uses a different system for newfound stars. Most consist of an abbreviation that stands for either the type of star or a catalog that lists information about the star, followed by a group of symbols. For instance, PSR J1302-6350 is a pulsar, thus the PSR. The J reveals that a coordinate system known as J2000 is being used, while the 1302 and 6350 are coordinates similar to the latitude and longitude codes used on Earth. A young, glittering collection of stars looks like an aerial burst. The cluster is surrounded by clouds of interstellar gas and dust—the raw material for new star formation.

The nebula, located 20,000 light-years away in the constellation Carina, contains a central cluster of huge, hot stars, called NGC 3603. Credit: NASA, ESA, R., F. Paresce, E. Young, the WFC3 Science Oversight Committee, and the Hubble Heritage Team Star formation A star develops from a giant, slowly rotating cloud that is made up entirely or almost entirely of hydrogen and helium. Due to its own gravitational pull, the cloud behind to collapse inward, and as it shrinks, it spins more and more quickly, with the outer parts becoming a disk while the innermost parts become a roughly spherical clump. According to NASA, this collapsing material grows hotter and denser, forming a ball-shaped protostar . When the heat and pressure in the protostar reaches about 1.8 million degrees Fahrenheit (1 million degrees Celsius), atomic nuclei that normally repel each other start fusing together, and the star ignites.

Nuclear fusion converts a small amount of the mass of these atoms into extraordinary amounts of energy — for instance, 1 gram of mass converted entirely to energy would be equal to an explosion of roughly 22,000 tons of TNT. Evolution of stars The life cycles of stars follow patterns based mostly on their initial mass. These include intermediate-mass stars such as the sun, with half to eight times the mass of the sun, high-mass stars that are more than eight solar masses, and low-mass stars a tenth to half a solar mass in size. The greater a star's mass, the shorter its lifespan generally is. Objects smaller than a tenth of a solar mass do not have enough gravitational pull to ignite nuclear fusion — some might become failed stars known as brown dwarfs . An intermediate-mass star begins with a cloud that takes about 100,000 years to collapse into a protostar with a surface temperature of about 6,750 F (3,725 C). After hydrogen fusion starts, the result is a T-Tauri star , a variable star that fluctuates in brightness.

This star continues to collapse for roughly 10 million years until its expansion due to energy generated by nuclear fusion is balanced by its contraction from gravity, after which point it becomes a main-sequence star that gets all its energy from hydrogen fusion in its core. The greater the mass of such a star, the more quickly it will use its hydrogen fuel and the shorter it stays on the main sequence. After all the hydrogen in the core is fused into helium, the star changes rapidly — without nuclear radiation to resist it, gravity immediately crushes matter down into the star's core, quickly heating the star. This causes the star's outer layers to expand enormously and to cool and glow red as they do so, rendering the star a red giant . Helium starts fusing together in the core, and once the helium is gone, the core contracts and becomes hotter, once more expanding the star but making it bluer and brighter than before, blowing away its outermost layers. After the expanding shells of gas fade, the remaining core is left, a white dwarf that consists mostly of carbon and oxygen with an initial temperature of roughly 180,000 degrees F (100,000 degrees C).

Since white dwarves have no fuel left for fusion, they grow cooler and cooler over billions of years to become black dwarves too faint to detect. (Our sun should leave the main sequence in about 5 billion years.) A high-mass star forms and dies quickly. These stars form from protostars in just 10,000 to 100,000 years. While on the main sequence, they are hot and blue, some 1,000 to 1 million times as luminous as the sun and are roughly 10 times wider. When they leave the main sequence, they become a bright red supergiant, and eventually become hot enough to fuse carbon into heavier elements. After some 10,000 years of such fusion, the result is an iron core roughly 3,800 miles wide (6,000 km), and since any more fusion would consume energy instead of liberating it, the star is doomed, as its nuclear radiation can no longer resist the force of gravity. When a star reaches a mass of more than 1.4 solar masses, electron pressure cannot support the core against further collapse, according to NASA. The result is a supernova.

Gravity causes the core to collapse, making the core temperature rise to nearly 18 billion degrees F (10 billion degrees C), breaking the iron down into neutrons and neutrinos. In about one second, the core shrinks to about six miles (10 km) wide and rebounds just like a rubber ball that has been squeezed, sending a shock wave through the star that causes fusion to occur in the outlying layers. The star then explodes in a so-called Type II supernova. If the remaining stellar core was less than roughly three solar masses large, it becomes a neutron star made up nearly entirely of neutrons, and rotating neutron stars that beam out detectable radio pulses are known as pulsars. If the stellar core was larger than about three solar masses, no known force can support it against its own gravitational pull, and it collapses to form a black hole . A low-mass star uses hydrogen fuel so sluggishly that they can shine as main-sequence stars for 100 billion to 1 trillion years — since the universe is only about 13.7 billion years old , according to NASA, this means no low-mass star has ever died.

Still, astronomers calculate these stars, known as red dwarfs , will never fuse anything but hydrogen, which means they will never become red giants. Instead, they should eventually just cool to become white dwarfs and then black dwarves. Constellations ancient and modern grace the skies year round. Let's see what you know about the star patterns that appear overhead every night. Astro 1A Midterm #2 Sample Questions 1. Granulation on the surface of the Sun is caused by A. magnetic field disturbances above the solar surface. B. nuclear fusion processes occurring just beneath the surface. C. differential rotation of the fluid surface. D. convective currents carrying heat from beneath the surface. ï¿½ 2. What is a spicule on the Sun? A. a jet of rising gas in the chromosphere B. a long, thin, curved line of bright gas in the corona C. a bright arc of gas suspended above the edge of the visible disk of the Sun D. a small, bright cell in the photosphere ï¿½ 3. Which of the following four spectral-luminosity classes would correspond to a red supergiant? A. B7 I D.

1/4 as bright ï¿½ 5. What is the dominant mechanism by which energy is transported through the interior of the Sun? A. by photons (radiative transport of energy) B. by collisions of faster-moving particles with slower-moving particles (conductive transport of energy) C. by neutrinos streaming outward through the Sun's material (particle transport of energy) D. by hotter gas rising and cooler gas falling (convective transport of energy) ï¿½ 6. Hydrogen "burning" by fusion reactions occurs only in the deep interior of the Sun (and other stars), because this is the only place in the Sun where A. there is sufficient hydrogen. B. the density is sufficiently low for the high temperature atoms to build up enough energy to collide and undergo fusion. C. the temperature is low enough and the density is high enough to allow hydrogen atoms to collide with each other often enough for fusion to occur. D. the requisite conditions of high temperature and high density occur. ï¿½ 7. What condition is considered sufficient for an interstellar cloud to collapse and form a star or stars (i.e., if this condition holds then the cloud has to collapse)? A.

The cloud must be alone in space, far from the gravitational influence of stars or other interstellar clouds. B. The cloud must be cooler than 100 K. C. Gravity must be strong enough to reach all parts of the cloud. D. Gravity must dominate gas pressure inside the cloud. ï¿½ 8. Stellar parallax exists because A. the Earth moves in space. B. stars move in space. C. the Earth rotates about its own axis. D. stars have size (they are not really just points of light). ï¿½ 9. A nova is a sudden brightening of a star that occurs when A. material from a companion star is transferred onto the surface of a white dwarf in a binary system and is subsequently blasted into space by a runaway thermonuclear explosion, leaving the white dwarf intact to repeat the process. B. the electron-degenerate iron core of a massive star collapses after its mass becomes larger than the Chandrasekhar mass limit. C. material from a companion star is transferred onto a neutron star in a binary system, causing the neutron star to collapse into a black hole. D.

material from a companion star is transferred onto the surface of a white dwarf star in a binary system, after which runaway carbon fusion reactions cause the entire white dwarf to be destroyed in an explosion. ï¿½ 10. The Sun has existed for a very long time without change in its size, appearance, or behavior. This means that it must be in hydrostatic equilibrium. Under these conditions, which two parameters must be in exact balance within the Sun? A. numbers of hydrogen and helium nuclei B. hydrogen gas pressure and helium gas pressure C. inward force of gravity and outward gas pressure D. magnetic field and force of gravity ï¿½ 11. Why should you NEVER look directly at the Sun? A. It uses up valuable time. B. Looking directly at the Sun causes blindness. C. It can lead to baldness. D. It is bad for the complexion. ï¿½ 12. In terms of nuclear reactions, what is the next stage of a star's life after the end of hydrogen burning in the core? A. hydrogen burning in a thin shell around the core B. helium burning in the core C. carbon burning D.

death (it becomes either a supernova or a white dwarf) ï¿½ 13. At which phase of its evolutionary life is a white dwarf star? A. very late for a small mass star, the dying phase B. just at the main-sequence phase C. early phase, soon after formation D. post-supernova phase, the remnant of the explosion ï¿½ 14. Observations of the spectrum of the solar corona reveal emission lines that come from atoms from which many electrons have been stripped. What conclusion can be drawn from this result? A. The solar rotation speed at coronal height reduces the ability of atoms to retain electrons. B. The pressure of the gas is sufficient to squeeze the electrons from the atoms. C. The magnetic field intensity is high enough to drag electrons from the atoms. D. The gas temperatures are extremely high. ï¿½ 15. The star Alphard has an apparent magnitude of 2.0, and the star Megrez has an apparent magnitude of 3.3. The only thing that can be said with certainty about Alphard is that it A. is brighter than Megrez, as seen in our sky. B.

has a greater luminosity than Megrez. C. is closer than Megrez. D. is fainter than Megrez, as seen in our sky. ï¿½ 16. The total time that the Sun will spend converting hydrogen to helium in its core is A. less than 1 million years. B. at least 200 billion years (2 ï¿½ 1011) years. C. about 4.5 million years. D. about 10 billion years (1010 years). ï¿½ 17. What happens to the surface of a low-mass star after the helium core and helium shell nuclear fusion "burning" stages are completed? A. It stabilizes at the size of a red giant star, the radiation pressure from below balancing gravity from the core, to cool slowly for the rest of its life. B. It is propelled slowly away from the core to form a planetary nebula. C. It is spun off into space to form a spiral galaxy. D. It contracts back onto the core and becomes hot enough to undergo further hydrogen fusion, leading to a very hot and active white dwarf star. ï¿½ ï¿½ 18.

In some binary star systems, such as Algol, the less massive star is a red giant and the more massive star is on the main sequence. This is evidence that A. mass transfer has occurred from one star to another. B. the more massive star formed later, from a disk of gas surrounding the less massive star. C. the more massive star captured the other one into orbit some time after the two stars had formed. D. stars evolve differently in binary star systems, with less massive stars evolving faster than more massive stars. ï¿½ 19. A white dwarf star, as it evolves, undergoes which of the following changes? A. Luminosity and size decrease, while its temperature remains constant. B. Its temperature remains constant, but its radius and luminosity decrease. C. It shrinks in size, the resulting release of gravitational energy maintaining both luminosity and temperature constant. D. Luminosity and temperature decrease, but its size remains constant. ï¿½ 20. What process provides the power for the Sun? A. fusion of helium into carbon B. fission of uranium to form lead C. emission of neutrinos D. fusion of hydrogen into helium ï¿½ 21.

What is the structure of a typical large sunspot? A. an irregular dark area of uniform darkness B. a dark center surrounded by a less dark area C. a roughly circular, dark region with a lighter central area D. usually round and of uniform darkness ï¿½ 22. If you were to look at one kilogram of material taken from the surface of the Sun and 1 kilogram taken from the center, which of the following statements would be true of these two 1 kilogram masses? A. The kilogram from the surface would contain more hydrogen than the one from the center. B. Neither of them would contain any hydrogen. C. They both would contain the same amount of hydrogen. D. The kilogram from the surface would contain less hydrogen than the one from the center. ï¿½ 23. What is the size of a star in the upper right part of the Hertzsprung-Russell diagram compared to one in the middle of the diagram? A. It is fainter. C. There are no stars in the upper right part of the diagram. D. It is larger. ï¿½ 24.

What is the physical reason for the appearance of periodic splitting and recombining of spectral lines in the spectra of binary stars? A. distortion of atoms on one star by the gravitational force of the other star, leading to line splitting B. Zeeman splitting of spectral lines on one star by the magnetic field of the second star C. oscillations on the surfaces of the stars leading to Doppler-shifted lines D. Doppler shift of light from stars orbiting each other, moving toward and away from Earth during this orbital motion ï¿½ 25. All stars on the main sequence A. are at a late stage of evolution after the red giant stage. B. are changing slowly in size by gravitational contraction. C. generate energy by hydrogen fusion in their centers. D. have approximately the same age to within a few million years. ï¿½ 26. What is the most important quantity on which the lifetime of a star depends? A. temperature of the star's corona B. abundance of heavy elements in the star C. star's speed of rotation D. mass of the star ï¿½ 27. Two stars in our sky have the same apparent brightness.

If neither of them is hidden behind gas or dust clouds, then we know that they A. may be at different distances, in which case the nearest one must have the greater luminosity. B. may be at different distances, in which case the farther one must have the greater luminosity. C. must have the same temperature. D. must be at the same distance away from us. ï¿½ 28. At what stage of evolution are the horizontal-branch stars, which have similar luminosities between 50 and 100 times that of the Sun but a range of temperatures? A. because the horizontal branch is part of the main sequence, these stars are in the main-sequence stage B. white dwarf stage C. postï¿½main-sequence stage D. preï¿½main-sequence stage, evolving toward the main sequence ï¿½ 29. The smallest mass that a main sequence star can have is about 0.08 solar mass. The reason for this is that A. the temperature in the core of a contracting protostar of less than 0.08 solar masses does not get high enough for nuclear reactions to start. B.

protostars cannot form with masses less than 0.08 solar mass. C. thermonuclear reactions begin so suddenly in stars of less than 0.08 solar mass, that the star is disrupted by an explosion. D. protostars of less than 0.08 solar masses are not massive enough to contract. ï¿½ 30. The helium flash is another name for A. the sudden appearance of helium during a supernova explosion (explosion of a star at the end of its life). B. a sudden onset of helium fusion reactions in red giant and supergiant stars of any mass. C. a sudden release of energy at the end of helium burning, due to core contraction. D. a sudden onset of helium fusion reactions in the core of a low-mass red giant star. ï¿½ 31. Given the magnitudes below, which of the following stars is the brightest? A. 0.1ï¿½ B. 1.4ï¿½ï¿½ C. 5.6ï¿½ï¿½ D. 2.3 32. Small, hot, low luminosity stars are called A. supergiantsï¿½ï¿½ B.

white dwarfsï¿½ï¿½ C. red giantsï¿½ D. main sequence stars 33. Given the magnitudes below, which of the following stars could NOT be seen with the naked eye? A. 3.7ï¿½ï¿½ B. 1.8ï¿½ï¿½ C. 6.9ï¿½ï¿½ D. 2.4 34. Which stage in a low mass star's life will life on the surface of the Earth be extinguished? A. red supergiantï¿½ï¿½ Bï¿½ main sequenceï¿½ï¿½ C. red giantï¿½ï¿½ D. protostar 35. Which kind of nebula is heated by hot, young massive stars? A. Diffuseï¿½ï¿½ B. Darkï¿½ï¿½ C. Reflectionï¿½ï¿½ D. Emission 36. Helium fuses at a higher temperature than hydrogen because A. there is more repulsion between two helium nuclei B. the helium nuclei are more massive C. the helium nuclei are less massive D. there is less repulsion between two helium nuclei 37.

Place the three atmospheric layers of the Sun in order of increasing temperature. A. photosphere, chromosphere, corona D. OBAFGKM 43. The Hertzsprung-Russell diagram is a statistical plot of which of the following two stellar parameters? A. luminosity and surface temperature B. radius and mass D. mass and surface temperature 44. The most likely places in which stars and planetary systems are forming in the universe are A. the rarified outer space between galaxies. B. regions of hot gas in the spiral arms of galaxies. C. gas and dust nebulae. D. the centers of galaxies. A. that are slowly contracting and cooling. B. whose surfaces are slowly expanding while their cores are contracting. C. that are slowly contracting and heating up. D. that are slowly heating up and expanding. 46. At what stage of its evolutionary life is the Sun? A. post-main sequenceï¿½red giant (cool) phase B. before main sequenceï¿½protostar C. main sequenceï¿½middle age D. just before supernova stage 47.

Compared to the composition of the early Sun, the composition of the gas in the core of a red giant star is A. very different, with lots of H but almost no He after thermonuclear fusion. B. very different, because thermonuclear fusion has transformed all the H and He into heavier elements. C. significantly different, with a very high fraction of He and no H. D. the same, with a high fraction of H compared to He, because these stars were produced from the same initial material. 48. What is the last nuclear burning stage in the life of a low-mass star like the Sun? A. fusion of hydrogen nuclei to form helium B. fusion of silicon nuclei to form iron C. fusion of iron nuclei with protons and neutrons to form heavy elements D. fusion of helium nuclei to form carbon 49. A white dwarf is A. an object like Jupiter which was not massive enough to become a star. B. a low-mass star at the end of its life. C. a hot, main-sequence star. D. a type of protostar. 50.

From observations of supernova explosions in distant galaxies, it is predicted that there should be about one supernovae per century in our galaxy, whereas we have seen only about one every 300 years from Earth. Why is this? A. Most supernovae occur in the Milky Way, which can be seen only from the southern hemisphere where, until recently, there were no observers of the sky. B. Our galaxy is peculiar in that the majority of stars are old, well beyond the supernova stages of evolution. C. The majority of supernovae produce no visible light, only radio and X-ray radiation, which we have only been able to observe for the past three decades. D. Most supernovae occur in the galactic plane where interstellar dust obscures our view of them from Earth. The Life of a Star The Life of a Star This page (as the title says) is all about the life of a star. It will show all the stages that a small star, and a massive star have to go through during their lifetime. We have all sorts of pics and links for you to look at and explore when you are just about ready to recieve that vast information that we have kindly put together. But we have one FAQ!

What is a Star? Stars are hot bodies of glowing gas that start their life in Nebulae. They vary in size, mass and temperature, diameters ranging from 450x smaller to over 1000x larger than that of the Sun. Masses range from a twentieth to over 50 solar masses and surface temperature can range from 3,000 degrees Celcius to over 50,000 degrees Celcius. The colour of a star is determined by its temperature, the hottest stars are blue and the coolest stars are red. The Sun has a surface temperature of 5,500 degrees Celcius, its colour appears yellow. The energy produced by the star is by nuclear fusion in the stars core. The brightness is measured in magnitude, the brighter the star the lower the magnitude goes down. There are two ways to measuring the brightness of a star, apparent magnitude is the brghtness seen from Earth, and absolute magnitude which is the brightness of a star seen from a standard distance of 10 parsecs (32.6 light years). Stars can be plotted on a graph using the Hertzsprung Russell Diagram (see picture below).

Hertzsrung Russell Diagram It shows that the temerature coincides with the luminosity, the hotter the star the higher the luminosity the star has. You can also tell the size of each star from the graph as the higher the radius the higher the temperature and luminosity. Small Stars- The Life of a Star of about one Solar Mass. Small stars have a mass upto one and a half times that of the Sun. Stage 1- Stars are born in a region of high density Nebula, and condenses into a huge globule of gas and dust and contracts under its own gravity. This image shows the Orion Nebula or M42 . Stage 2 - A region of condensing matter will begin to heat up and start to glow forming Protostars. If a protostar contains enough matter the central temperature reaches 15 million degrees centigrade. This image is the outflow (coloured red)and protostar. Stage 3 - At this temperature, nuclear reactions in which hydrogen fuses to form helium can start. Stage 4 - The star begins to release energy, stopping it from contracting even more and causes it to shine. It is now a Main Sequence Star.

The nearest main sequence star to Earth, the Sun Stage 5 - A star of one solar mass remains in main sequence for about 10 billion years, until all of the hydrogen has fused to form helium. Stage 6 - The helium core now starts to contract further and reactions begin to occur in a shell around the core. Stage 7 - The core is hot enough for the helium to fuse to form carbon. The outer layers begin to expand, cool and shine less brightly. The expanding star is now called a Red Giant. The star expands to a Red Giant, below Stage 8 - The helium core runs out, and the outer layers drift of away from the core as a gaseous shell, this gas that surrounds the core is called a Planetary Nebula. A Planetary Nebula (Below, NGC 6543 ). Stage 9 - The remaining core (thats 80% of the original star) is now in its final stages. The core becomes a White Dwarf the star eventually cools and dims. When it stops shining, the now dead star is called a Black Dwarf.

Massive Stars - The Life of a Star of about 10 Solar Masses Massive stars have a mass 3x times that of the Sun. Some are 50x that of the Sun Stage 1 - Massive stars evolve in a simlar way to a small stars until it reaces its main sequence stage (see small stars, stages 1-4). The stars shine steadily until the hydrogen has fused to form helium ( it takes billions of years in a small star, but only millions in a massive star). Stage 2 - The massive star then becomes a Red Supergiant and starts of with a helium core surrounded by a shell of cooling, expanding gas. The massive star is much bigger in its expanding stage. (A Red Supergiant,below). Stage 3 - In the next million years a series of nuclear reactions occur forming different elements in shells around the iron core. Stage 4 - The core collapses in less than a second, causing an explosion called a Supernova, in which a shock wave blows of the outer layers of the star. (The actual supernova shines brighter than the entire galaxy for a short time).

The set of images below shows the star going into a stage called Supernova and contracting to become a neutron star The images above were from the HEASARC Homepage Stage 5 - Sometimes the core survives the explosion. If the surviving core is between 1.5 - 3 solar masses it contracts to become a a tiny, very dense Neutron Star. If the core is much greater than 3 solar masses, the core contracts to become a Black Hole. Red Giant Stars: Facts, Definition & the Future of the Sun Red Giant Stars: Facts, Definition & the Future of the Sun By Nola Taylor Redd, Space.com Contributor | August 21, 2013 06:00pm ET MORE Expanding red giant stars will swallow too-close planets. In the solar system, the sun will engulf Mercury and Venus, and may devour Earth, as well. Credit: James Gitlin/STScI AVL A red giant star is a dying star in the last stages of stellar evolution. In only a few billion years, our own sun will turn into a red giant star, expand and engulf the inner planets, possibly even Earth. What does the future hold for the light of our solar system and others like it?

Forming a giant Most of the stars in the universe are main sequence stars — those converting hydrogen into helium via nuclear fusion . A main sequence star may have a mass between a third to eight times that of the sun and eventually burn through the hydrogen in its core. Over its life, the outward pressure of fusion has balanced against the inward pressure of gravity. Once the fusion stops, gravity takes the lead and compresses the star smaller and tighter. Temperatures increase with the contraction, eventually reaching levels where helium is able to fuse into carbon. Depending on the mass of the star, the helium burning might be gradual or might begin with an explosive flash. The energy produced by the helium fusion causes the star to expand outward to many times its original size. Red giant stars reach sizes of 100 million to 1 billion kilometers in diameter (62 million to 621 million miles), 100 to 1,000 times the size of the sun today.

Because the energy is spread across a larger area, surface temperatures are actually cooler, reaching only 2,200 to 3,200 degrees Celsius (4,000 to 5,800 degrees Fahrenheit), a little over half as hot as the sun. This temperature change causes stars to shine in the redder part of the spectrum, leading to the name red giant, though they are often more orangish in appearance. This picture of the dramatic nebula around the bright red supergiant star Betelgeuse was created from images taken with the VISIR infrared camera on ESO’s Very Large Telescope (VLT). This structure, resembling flames emanating from the star, forms because the behemoth is shedding its material into space. Credit: ESO/P. Kervella Stars spend approximately a few thousand to 1 billion years as a red giant. Eventually, the helium in the core runs out and fusion stops. The star shrinks again until a new helium shell reaches the core. When the helium ignites, the outer layers of the star are blown off in huge clouds of gas and dust known as planetary nebulae . The core continues to collapse in on itself.

Smaller stars such as the sun end their lives as compact white dwarfs. The material of larger, more massive stars fall inward until the star eventually becomes a supernova , blowing off gas and dust in a dramatic fiery death. [ Amazing Photos of Supernova Explosions ] Though they look serene and silent from our vantage on Earth, stars are actually roiling balls of violent plasma. Test your stellar smarts with this quiz. Stars | Science Mission Directorate Science Mission Directorate Exoplanets Stars Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy. Star Formation Stars are born within the clouds of dust and scattered throughout most galaxies. A familiar example of such as a dust cloud is the Orion Nebula.

Turbulence deep within these clouds gives rise to knots with sufficient mass that the gas and dust can begin to collapse under its own gravitational attraction. As the cloud collapses, the material at the center begins to heat up. Known as a protostar, it is this hot core at the heart of the collapsing cloud that will one day become a star. Three-dimensional computer models of star formation predict that the spinning clouds of collapsing gas and dust may break up into two or three blobs; this would explain why the majority the stars in the Milky Way are paired or in groups of multiple stars. The observations of Eta Carinae's light echo are providing new insight into the behavior of powerful massive stars on the brink of detonation. Credit: NOAO, AURA, NSF, and N. Smith (University of Arizona) As the cloud collapses, a dense, hot core forms and begins gathering dust and gas. Not all of this material ends up as part of a star — the remaining dust can become planets, asteroids, or comets or may remain as dust. In some cases, the cloud may not collapse at a steady pace.

In January 2004, an amateur astronomer, James McNeil, discovered a small nebula that appeared unexpectedly near the nebula Messier 78, in the constellation of Orion. When observers around the world pointed their instruments at McNeil's Nebula , they found something interesting — its brightness appears to vary. Observations with NASA's Chandra X-ray Observatory provided a likely explanation: the interaction between the young star's magnetic field and the surrounding gas causes episodic increases in brightness. Main Sequence Stars A star the size of our Sun requires about 50 million years to mature from the beginning of the collapse to adulthood. Our Sun will stay in this mature phase (on the main sequence as shown in the Hertzsprung-Russell Diagram) for approximately 10 billion years. Stars are fueled by the nuclear fusion of hydrogen to form helium deep in their interiors. The outflow of energy from the central regions of the star provides the pressure necessary to keep the star from collapsing under its own weight, and the energy by which it shines. As shown in the Hertzsprung-Russell Diagram, Main Sequence stars span a wide range of luminosities and colors, and can be classified according to those characteristics.

The smallest stars, known as red dwarfs, may contain as little as 10% the mass of the Sun and emit only 0.01% as much energy, glowing feebly at temperatures between 3000-4000K. Despite their diminutive nature, red dwarfs are by far the most numerous stars in the Universe and have lifespans of tens of billions of years. On the other hand, the most massive stars, known as hypergiants, may be 100 or more times more massive than the Sun, and have surface temperatures of more than 30,000 K. Hypergiants emit hundreds of thousands of times more energy than the Sun, but have lifetimes of only a few million years. Although extreme stars such as these are believed to have been common in the early Universe, today they are extremely rare - the entire Milky Way galaxy contains only a handful of hypergiants. Stars and Their Fates In general, the larger a star, the shorter its life, although all but the most massive stars live for billions of years. When a star has fused all the hydrogen in its core, nuclear reactions cease.

Deprived of the energy production needed to support it, the core begins to collapse into itself and becomes much hotter. Hydrogen is still available outside the core, so hydrogen fusion continues in a shell surrounding the core. The increasingly hot core also pushes the outer layers of the star outward, causing them to expand and cool, transforming the star into a red giant. If the star is sufficiently massive, the collapsing core may become hot enough to support more exotic nuclear reactions that consume helium and produce a variety of heavier elements up to iron. However, such reactions offer only a temporary reprieve. Gradually, the star's internal nuclear fires become increasingly unstable - sometimes burning furiously, other times dying down. These variations cause the star to pulsate and throw off its outer layers, enshrouding itself in a cocoon of gas and dust. What happens next depends on the size of the core. Average Stars Become White Dwarfs For average stars like the Sun, the process of ejecting its outer layers continues until the stellar core is exposed. This dead, but still ferociously hot stellar cinder is called a White Dwarf .

White dwarfs, which are roughly the size of our Earth despite containing the mass of a star, once puzzled astronomers - why didn't they collapse further? What force supported the mass of the core? Quantum mechanics provided the explanation. Pressure from fast moving electrons keeps these stars from collapsing. The more massive the core, the denser the white dwarf that is formed. Thus, the smaller a white dwarf is in diameter, the larger it is in mass! These paradoxical stars are very common - our own Sun will be a white dwarf billions of years from now. White dwarfs are intrinsically very faint because they are so small and, lacking a source of energy production, they fade into oblivion as they gradually cool down. This fate awaits only those stars with a mass up to about 1.4 times the mass of our Sun. Above that mass, electron pressure cannot support the core against further collapse. Such stars suffer a different fate as described below. White Dwarfs May Become Novae If a white dwarf forms in a binary or multiple star system, it may experience a more eventful demise as a nova. Nova is Latin for "new" - novae were once thought to be new stars.

Today, we understand that they are in fact, very old stars - white dwarfs. If a white dwarf is close enough to a companion star, its gravity may drag matter - mostly hydrogen - from the outer layers of that star onto itself, building up its surface layer. When enough hydrogen has accumulated on the surface, a burst of nuclear fusion occurs, causing the white dwarf to brighten substantially and expel the remaining material. Within a few days, the glow subsides and the cycle starts again. Sometimes, particularly massive white dwarfs (those near the 1.4 solar mass limit mentioned above) may accrete so much mass in the manner that they collapse and explode completely, becoming what is known as a supernova. Supernovae Leave Behind Neutron Stars or Black Holes Main sequence stars over eight solar masses are destined to die in a titanic explosion called a supernova . A supernova is not merely a bigger nova. In a nova, only the star's surface explodes. In a supernova, the star's core collapses and then explodes. In massive stars, a complex series of nuclear reactions leads to the production of iron in the core.

Having achieved iron, the star has wrung all the energy it can out of nuclear fusion - fusion reactions that form elements heavier than iron actually consume energy rather than produce it. The star no longer has any way to support its own mass, and the iron core collapses. In just a matter of seconds the core shrinks from roughly 5000 miles across to just a dozen, and the temperature spikes 100 billion degrees or more. The outer layers of the star initially begin to collapse along with the core, but rebound with the enormous release of energy and are thrown violently outward. Supernovae release an almost unimaginable amount of energy. For a period of days to weeks, a supernova may outshine an entire galaxy. Likewise, all the naturally occurring elements and a rich array of subatomic particles are produced in these explosions. On average, a supernova explosion occurs about once every hundred years in the typical galaxy. About 25 to 50 supernovae are discovered each year in other galaxies, but most are too far away to be seen without a telescope.

Neutron Stars If the collapsing stellar core at the center of a supernova contains between about 1.4 and 3 solar masses, the collapse continues until electrons and protons combine to form neutrons, producing a neutron star . Neutron stars are incredibly dense - similar to the density of an atomic nucleus. Because it contains so much mass packed into such a small volume, the gravitation at the surface of a neutron star is immense. Like the White Dwarf stars above, if a neutron star forms in a multiple star system it can accrete gas by stripping it off any nearby companions. The Rossi X-Ray Timing Explorer has captured telltale X-Ray emissions of gas swirling just a few miles from the surface of a neutron star. Neutron stars also have powerful magnetic fields which can accelerate atomic particles around its magnetic poles producing powerful beams of radiation. Those beams sweep around like massive searchlight beams as the star rotates. If such a beam is oriented so that it periodically points toward the Earth, we observe it as regular pulses of radiation that occur whenever the magnetic pole sweeps past the line of sight. In this case, the neutron star is known as a pulsar.

Black Holes If the collapsed stellar core is larger than three solar masses, it collapses completely to form a black hole: an infinitely dense object whose gravity is so strong that nothing can escape its immediate proximity, not even light. Since photons are what our instruments are designed to see, black holes can only be detected indirectly. Indirect observations are possible because the gravitational field of a black hole is so powerful that any nearby material - often the outer layers of a companion star - is caught up and dragged in. As matter spirals into a black hole, it forms a disk that is heated to enormous temperatures, emitting copious quantities of X-rays and Gamma-rays that indicate the presence of the underlying hidden companion. From the Remains, New Stars Arise The dust and debris left behind by novae and supernovae eventually blend with the surrounding interstellar gas and dust, enriching it with the heavy elements and chemical compounds produced during stellar death. Eventually, those materials are recycled, providing the building blocks for a new generation of stars and accompanying planetary systems.

Question: What is the name given to a small hot dying star
Answer: White dwarf